Meditation in simple word is focusing at one point, or awareness at any one point, the point can be outer object (and object, point, lamp) or inner subtle things like breath, chakra, enegy...
The goal is to maintain that awareness for a very long period without breaking it.
For this patanjali say when you focus or be aware of any object its dharna, in dharna the flow of awareness will break but when the flow of awareness on a particular point become continous for longer period it becomes dhyana that is meditation...
Continous Flow of awareness is mediation...